This beautiful, fairly isolated trail leads to a pristine subalpine basin with streams, wildlife, and Thunder Lake. The lake has multiple campsites along its northern shore, and the fishing in the lake and its inlet and outlet is very good.

Starting at the often-busy Wild Basin TH, the trail passes through dense forests as it follows the North Fork of the Saint Vrain River through the southernmost section of Rocky Mountain National Park. The trail passes alongside the small Copeland Falls before continuing west towards Calypso Cascades, Ouzel Falls and the Thunder Lake cutoff (though the backcountry campsite cutoff can save hikers short on time nearly a mile of walking each way-just follow the signs to Pine Ridge, Tahosa and Aspen Knoll campsites before reaching Calypso Cascades. While this cutoff saves time and is pleasantly isolated from the crowds, it does miss the beautiful Calypso Cascades and Ouzel Falls). This section of the trail is mild, and can be very busy on Fridays and Saturdays throughout the summer. By avoiding peak times or getting an early start to the hike, even this section of trail can be quiet and beautiful, and the river along the trail could hardly be more beautiful.

After passing by Ouzel Falls, continue for about a quarter mile before splitting right at the well-marked Thunder Lake fork. This section of trail will continue uphill for nearly a mile before joining up with the aforementioned backcountry campsite trail. Continue up this remote canyon for 1.3 miles before passing the Lion Lake 1 trail split. From this point, Thunder Lake is about a mile and a half away. A majority of this will be up a somewhat steep incline with occasional views of the underrated Mertensia Falls leading out of the Eagle Lake drainage.

The final half mile passes through a level meadow and along a couple of streams and brooks that lead out of the cirques belonging to Thunder Lake, the Lion Lakes and Falcon Lake. The final approach to the lake curves downhill from the group campsite split. By following the trail to these sites, you will come to the picturesque 1930's ranger cabin which sits just a few hundred feet from the Eastern shore of the lake. A nice trail follows along the northern shore to the inlet and a series of waterfalls above the lake. During the spring, some of the largest Greenback Cutthroat in the park can be seen spawning. Please avoid disturbing these fish during their fragile spawning period. The area surrounding the lake is beautiful, and if you have time, wander around and explore one of the most remote areas of RMNP! Tanima Peak rises above the Southern shore of the lake, while Pilot Mountain and Mount Alice rise to the West and North of Thunder Lake.

The lake is about six miles (each way) from the trailhead, and if you are using the National Geographic Rocky Mountain National Park Topographical Map, watch out for a bunch of incorrect trail distances! Two or three of the labeled distances seem to be miscalculations and lead hikers to believe they are closer than they think.

Pack List

Enough water for a full day of hiking

Trail map and compass

Extra layers (the lake can get windy and cold)

Rain jacket

Decent hiking/trail running shoes

Plenty of snacks

Camera

First aid kit

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